In order to master the time-space evolution law of the stress field and the hydraulic pressure field near the fracturing boreholes during the hydraulic fracturing process of the coal mass,the physical simulation test system of the multi-field coupling coal bed methane mining was applied to the experiment study.The test results showed that the full process of the hydraulic fracturing could be divided into four stages and they were stress accumulated stage,micro crack development stage,fracture stability lost and expansion stage and after the cracking stage.During the hydraulic fracturing process,the radial stress of the fractured borehole would be varied obviously and the stress variation parallel to the direction of the fractured borehole would not be obvious.Within the crack expanded scope,the location with a distance more far to the fractured section would be late to have a stress increased.During the hydraulic fracturing process,the hydraulic pressure field evolution would have a closed relationship to the crack development and expansion.The hydraulic pressure isoline would be inclined to be developed along the direction of the crack expansion.The expansion speed of the hydraulic pressure isoline along the maximum principal stress direction would be higher than the expansion speed along the direction of the central principal stress and minimum principal stress,which shows that the hydraulic fracturing crack is mainly along the maximum principal stress direction.%为了掌握煤体水力压裂过程中压裂孔附近应力场、水压力场的时空演化规律,利用多场耦合煤层气开采物理模拟试验系统进行试验研究.试验结果表明:水力压裂全过程可以分为4个阶段,分别为应力积累阶段、微破裂发育阶段、裂缝失稳扩展阶段、破裂后阶段;在水力压裂过程中压裂孔径向应力会发生显著变化,而平行于压裂孔方向的应力变化不明显,且在裂缝扩展范围内距离压裂段越远的位置发生应力升高的时间越晚;水力压裂过程中水压力场的演化与裂缝的发育、扩展有着密切的联系,水压力等值线更倾向于沿着裂缝扩展的方向发展,且水压力等值线沿最大主应力方向的扩展速度明显大于沿中间主应力和最小主应力方向的扩展速度,表明水力压裂裂缝主要沿最大主应力方向扩展.
展开▼
